It is known to produce a transparent optical component by forming a set of cells which are separate and juxtaposed parallel to a surface of the component (FR 2 872 259). Each cell is filled with a suitable optical material, so that the set of cells thus filled confers on the component a desired optical function. For example, the function of the component may be an optical power when the material which is contained in the cells has a variable optical refractive index. It may also be a protection against the sun when the optical material is absorbing, or may reinforce contrast when it is polarizing. The use of separate cells makes it possible to easily vary the intensity of the optical function of the component along the surface of the latter. Optionally, the optical material which is contained in the cells may also be an electro-active material, so that the optical function of the component can be controlled by an electrical command.
Such a method for the production of a transparent optical component is advantageous, in particular because it allows using of a same base component with cells in order to obtain final components which have different optical functions. These different functions are obtained by modifying the material or materials contained in the cells. One same base component model having cells can then be used for a large number of final optical components. It is then manufactured on a large scale, which contributes to reducing the cost price of each optical component.
Such a method is also advantageous because it makes it possible to customize the optical component easily according to its future user. The customization is carried out by adapting the optical material which is contained in the cells of the component according to characteristics determined specifically for this user. Such a customization is particularly suitable when the optical component is an ophthalmic lens, intended for an identified spectacle wearer.
Now filling the cells of such a component with optical material is likely to create a regular, even periodic variation on the surface of this component. For example, when the optical material is liquid, a meniscus can form at the opening section of each cell through which the filling is carried out. Other phenomena linked to the filling of the cells can also cause a regular or periodic variation. Such a variation, even if slight, can then result in light diffusion which reduces the transparency of the optical component and to introduces defects in the image, such as for example ghost images, if the variations are periodic.
Within the meaning of the invention, an optical component is considered to be transparent when an image which is observed through this component is perceived without significant loss of contrast. In other words, the interposition of the transparent optical component between the image and an observer of the latter does not significantly reduce the quality of the image. In particular, diffraction is defined as the phenomenon of light scattering that is observed when a light wave is materially limited (J-P. PEREZ—Optique, Fondements et applications—7th edition—DUNOD—October 2004, p. 262). If a regular variation is present on the component, it causes light diffraction. As a result of this diffraction, a point of light is no longer perceived as a point through the optical component. The resulting macroscopic diffusion, or incoherent diffusion, produces a milky appearance or diffusion halo, of the cell structure of the optical component. In particular, a point light source appears through the optical component as a disc of light, or as being encircled by one or more rings of light. This results in a loss of contrast of an image which is observed through the component. This loss of contrast is similar to a reduction in the transparency, as previously defined. When the diffracting objects are arranged periodically, a grating effect results, making diffraction orders appear. These diffraction orders give rise to unwanted images and reduce the contrast of the image and thus the transparency of the component. The image of a point light source is then encircled by small unwanted spots which are easily identified visually against a dark background, even if the fraction of the light energy distributed in these unwanted images is small.
Such a reduction in transparency is particularly unfavourable when the optical component is an ophthalmic lens, in particular a spectacles lens.